The Stem Cell and Tissue Culture Core will provide a centralized facility and capacity for cell line and hematopoietic stem cell purification, synchronization and culture for all participants in the Program Project. Specifically, the Core will provide a focused expertise in the maintenance of cells lines and a major emphasis on the purification of murine hematopoietic stem/progenitor cells. These purifications will be based on cell surface expression of phenotypic markers and the utilization of low staining with Rhodamine and Hoechst to define primitive quiescent cells. Purification procedures will make extensive use of the current fluorescent activated cell sorting core (BD FACS Star plus) and of a new research dedicated cell sorting core currently under development which will feature the MoFlo high speed cell sorter from Cytomation. This latter core will allow us to proceed with more developmental work with regard to cell sorting and will allow for higher speed sorting and experiments at all hours of the day and night. Cores will also develop and refine protocols for progenitor stem cell synchronization and transplantation. By consolidating cell culture activities in a single source the core will function ot standardized cell populations used in parallel by the various projects and will be able to provide individual projects with a uniform quality and consistent supply of cytokines and culture reagents. A critical feature of the core will be the provision of highly purified progenitor/stem cell populations to each of the projects and the development of new transplantation models.